Those batten reinforced tips are used by North on its kites. The idea of battens i saw first on the internet as a solution for the tips of the 5-strut Wipika airblast 8.4. Wipika solved it by adding two inflatable struts. The battens seem nicer!

I think you'll be able to read more there. The forum has a search option.

Another option is posting your question there. I'm sure you'll get a lot of response.

Yes battens work great, I was putting battens on my Old Free Airs when they first came out, I didn't fly them without them, Everyone thought I was crazy cutting off my tips and putting carbon battens in. I didn't understand why they didn't do it to begin with. On your Naish 15.5- try adding on about 4 inches to the width of the tip then put in a batten, then move your trailing edge hook up point out to the edge. All the kites I've mod. this way the person has said that they feel they have a new kite I have done many mods for a ton of folks to increase the kites control and make it easier to turn!! Not to mention putting on the extra hook up point to decrease control input , I did that to kites over a year ago. It all works, but if you design a kite with the correct amount of wing tip width to begin with you don't need that extra hook up point, its just a novelty.